Lead exposure in early childhood is an important cause of cognitive delay and behavior problems. In 1993, the National Institutes of Environmental Health Sciences with support from the NIH Office of Research on Minority Health initiated the Treatment of Lead-Exposed Children (TLC) Trial. That randomized, multi-center, placebo-controlled, double blind clinical trial was designed to assess the developmental benefits of oral chelation therapy, with a medication called succimer, for low-moderate levels of lead exposure before 33 months of age. CHOP has been one of four sites for enrollment and follow-up of children in the TLC Study. The present protocol, the Treatment of Lead-Exposed Children Follow-Up Study (TLC Plus), builds on the work of the initial TLC Study to determine whether chelation is effective in ameliorating the adverse impact of lead toxicity on neuropsychological functioning, behavior and social adjustment by assessing the children from the TLC Study at ages 7 and 7.5 years. Assessments of psychometric, psychoeducational, social-adaptive and neurological function will be made.